On 11/10/2023 14:26, Jianjun Wang wrote:
The size of translation table should be a power of 2, using fls() cannot
get the proper value when the size is not a power of 2. For example,
fls(0x3e00000) - 1 = 25, hence the PCIe translation window size will be
set to 0x2000000 instead of the expected size 0x3e00000. Fix translation
window by splitting the MMIO space to multiple tables if its size is not
a power of 2.
Hi Jianjun,
I've no knowledge in PCIE, so maybe what my suggestion is stupid:
Is it mandatory to fit the translation table size with 0x3e00000 (in
this example) ?
I'm asking because you can have an issue by reaching the maximum
translation table number.
Is it possible to just use only one table with the power of 2 size above
0x3e00000 => 0x4000000 ( fls(0x3e00000) = 26 = 0x4000000). The downside
of this method is wasting allocation space. AFAIK I already see this
kind of method for memory protection/allocation in embedded systems, so
I'm wondering if this method is safer than using multiple table for only
one size which isn't a power of 2.
--
Regards,
Alexandre
